Recently, a one-component developing method is typically used for small laser printers. From the viewpoints of costs (cost per page) and environmental burden of such small laser printers, a need exists for a toner (one-component developer) having low temperature fixability. In addition, a need exist for a developing roller, which has a low cost and a long life and which can be used for high speed development.
Conventional developing rollers tend to easily cause problems such that a film of components (such as external additives) of toner is formed on the surface of the developing rollers, thereby deteriorating the charging ability of the developing rollers or deteriorating reproducibility of solid toner images (this problem is hereinafter referred to as a toner filming problem); and the surface of the developing rollers is abraded due to friction between the toner and the developing rollers (this problem is hereinafter referred to as a roller abrasion problem). It is considered that these problems are prominently caused if a toner having low temperature fixability is used and the developing rollers are used for high speed development over a long period of time.
In attempting to prevent formation of a film of toner components and to improve image quality under high temperature and high humidity conditions, JP-2011-215467-A discloses a developing roller having a toner bearing layer including a fluorine-containing urethane resin so that the developing roller has good releasability from toner. However, when low temperature fixable toner is used in combination with such a developing roller, it is hard to prevent occurrence of the toner filming problem and the roller abrasion problem mentioned above.